如何让基类知道派生类属性？

Question

我正在尝试创建一个基类，用于以键/值方式存储数据。基类将生成密钥并负责存储数据。当继承基类时，派生类可以指定它自己的键，但基类必须知道派生类的键。例如：

public class ParentClass
{
   private string key = "Parent";

   public void GenerateKey()
   {
       Console.WriteLine(key);
   }
}

public class FeatureClass : ParentClass
{
   public string key = "Feature";

}

public class SubFeatureClass : FeatureClass 
{
   public string key = "SubFeature";

}

FeatureClass feature = new FeatureClass();
feature.GenerateKey(); //I would like this to produce "Parent_Feature"

SubFeatureClass subFeature = new SubFeatureClass();
subFeatureClass.GenerateKey(); //I would like this to generate "Parent_Feature_SubFeature"

无论发生了多少级别的继承，如何让基类知道其子级键。

Answer 1

您可以通过制作基本方法virtual并在覆盖中引用它来完成此操作：

public class ParentClass
{
   public virtual string key {get {return "Parent";}}

   public void GenerateKey()
   {
       Console.WriteLine(key);
   }
}

public class FeatureClass : ParentClass
{
   public override string key {get{return base.key +  "_Feature";}}

}

public class SubFeatureClass : FeatureClass 
{
   public override string key {get{return base.key +  "_SubFeature";}}

}

Answer 2

可以使用抽象或虚函数来实现这一点（哪一个取决于ParentClass是否适合作为实际类型或是否总是需要派生类。

在任何情况下，您都将拥有一个虚拟（或抽象）函数，您可以在派生类中重写该函数以返回特殊键。实际上，在C＃中，您可以拥有虚拟/抽象属性：

public abstract class ParentClass
{
   private string key = "Parent";

   protected abstract string derivedKey
   {
        get;
   }

   public void GenerateKey()
   {
       Console.WriteLine(key + derivedKey);
   }
}

public class FeatureClass : ParentClass
{
   public override string derivedKey
   {
        get
        {
             return "Feature";
        }
    }

}

Answer 3

您可以使用virtual属性

执行此操作

public class ParentClass
{
    public virtual string Key
    {
        get
        {
            return "Parent";
        }
    }
}

public class FeatureClass : ParentClass
{
    public override string Key
    {
        get
        {
            return base.Key + "_" + "Feature";
        }
    }

}

public class SubFeatureClass : FeatureClass 
{
    public override string Key
    {
        get
        {
            return base.Key + "_" + "SubFeature";
        }
    }
}

然后，您可以这样使用它，

FeatureClass feature = new FeatureClass();
Console.WriteLine(feature.Key); // <-- "Parent_Feature"

SubFeatureClass subFeature = new SubFeatureClass();
Console.WriteLine(subFeature.Key); // <-- "Parent_Feature_SubFeature"

Answer 4

使用虚拟财产而不是字段：

public class ParentClass
{
   public ParentClass(){Key = "Parent";}
   private virtual string Key {get;set;}

   public void GenerateKey()
   {
       Console.WriteLine(Key);
   }
}

public class FeatureClass : ParentClass
{
    public FeatureClass(){Key = base.Key + "_" + "Feature";}
    override string Key {get;set;}
}

Answer 5

public class ParentClass
{
    protected List<string> keys = new List<string>();

    public ParentClass()
    {
        keys.Add("Parent");
    }

    public void GenerateKey()
    {
        Console.WriteLine(string.Join("_", keys));
    }
}

public class FeatureClass : ParentClass
{
    public FeatureClass()
    {
        keys.Add("Feature");
    }
}

public class SubFeatureClass : FeatureClass
{
    public SubFeatureClass()
    {
        keys.Add("SubFeature");
    }

}

Answer 6

在我的版本中使用构造函数重载和构造函数链接：

public class ParentClass
{
    private string key;

    protected ParentClass(string childKeys)
    {
        key = !string.IsNullOrEmpty(childKeys) ? key + "Parent_" + childKeys : key;
    }

    public void GenerateKey()
    {
        // Get keys from subclasses
        Console.WriteLine(key);

    }
}

public class FeatureClass : ParentClass
{
    public FeatureClass() : base("Feature") { }
    protected FeatureClass(string key) : base("Feature_" + key) { }
}

public class SubFeatureClass : FeatureClass 
{
    public SubFeatureClass() : base("SubFeature") { }
    protected SubFeatureClass(string key) : base("SubFeature_" + key) { }
}

public class ReallySubFeatureClass : SubFeatureClass
{
    public ReallySubFeatureClass() : base("ReallySubFeature") { }
}

测试代码看起来与您的相似，但我添加了一个级别，例如：

class Program
{
    static void Main(string[] args)
    {
        FeatureClass feature = new FeatureClass();
        feature.GenerateKey(); //I would like this to produce "Parent_Feature"

        SubFeatureClass subFeature = new SubFeatureClass();
        subFeature.GenerateKey(); //I would like this to generate "Parent_Feature_SubFeature"

        ReallySubFeatureClass reallySubFeature = new ReallySubFeatureClass();
        reallySubFeature.GenerateKey();

        Console.ReadKey();
    }
}

<强>结果：